[TS] "Abstract methods can only appear within an abstract class" on "export default abstract class"

[gentoid]

Bug Report

• I would like to work on a fix!

Current behavior

I'm getting the Abstract methods can only appear within an abstract class. error on export default abstract class AbstractClass after bumping "@babel/core" from "7.12.10" to "7.12.13"

• I have a repo reproducing the behaviour

Input Code

Copied from the repro repo

abstract class WorkingAbstractClass {
    abstract test(): void;
}

class SomeClass extends WorkingAbstractClass {
    test(): void {
        console.log('ok!');
    }
}

export abstract class AbstractClassIsWorkingToo {
    abstract test(): void;
}

// this is the case where Babel raises the error
export default abstract class NotWorkingAbstractClass {
    abstract test(): void;
}

Expected behavior

I guess it should be according to the TS behaviour, i.e., this case should be allowable.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: .babelrc

Copied from the repro repo

{
    "presets": [
        "@babel/typescript"
    ]
}

Environment

  System:
    OS: Windows 10 10.0.18363
  Binaries:
    Node: 12.16.0 - ~\scoop\apps\nvm\current\nodejs\nodejs\node.EXE
    Yarn: 1.22.5 - ~\scoop\apps\yarn\current\Yarn\bin\yarn.CMD
    npm: 6.14.11 - ~\scoop\apps\yarn\current\global\node_modules\.bin\npm.CMD
  npmPackages:
    @babel/cli: ^7.12.13 => 7.12.13
    @babel/core: ^7.12.13 => 7.12.13
    @babel/preset-typescript: ^7.12.13 => 7.12.13

Possible Solution

Do not treat such cases as a syntax error

Additional context

[babel-bot]

Hey @gentoid! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

[Mrjeff578575]

the same issue

[nicolo-ribaudo]

Fixed in v7.12.14.

[forivall]

Was caused by #12686

[gentoid]

seems it wasn't published to the NPM registry

[nicolo-ribaudo]

https://www.npmjs.com/package/@babel/parser/v/7.12.14

[gentoid]

Ah, thanks. I wrongly checked @babel/core